/* Reads a 128 kB file into static data and "sorts" the bytes in
   it, using counting sort, a single-pass algorithm.  The sorted
   data is written back to the same file in-place. */

#include <debug.h>
#include <syscall.h>
#include "tests/lib.h"
#include "tests/main.h"

unsigned char buf[128 * 1024];
size_t histogram[256];

int main(int argc UNUSED, char *argv[])
{
    int handle;
    unsigned char *p;
    size_t size;
    size_t i;

    test_name = "child-sort";
    quiet = true;

    CHECK((handle = open(argv[1])) > 1, "open \"%s\"", argv[1]);

    size = read(handle, buf, sizeof buf);
    for (i = 0; i < size; i++)
        histogram[buf[i]]++;
    p = buf;
    for (i = 0; i < sizeof histogram / sizeof *histogram; i++)
    {
        size_t j = histogram[i];
        while (j-- > 0)
            *p++ = i;
    }
    seek(handle, 0);
    write(handle, buf, size);
    close(handle);

    return 123;
}
